Effects of Salinity on the Response of the Wetland Halophyte Kosteletzkya virginica (L.) Presl. to Copper Toxicity

Abstract

Kosteletzkya virginica (L.) Presl. is a perennial wetland halophyte which could be exposed to heavy metals in polluted salt marsh environments. In order to investigate the interaction between salinity (50 mM NaCl) and heavy metal, young plants were exposed in hydroponic culture to 10 μM Cu in the presence or absence of 50 mM NaCl. Copper strongly inhibited the leaf emergence and lateral branch development as well as leaf expansion, and induced a significant decrease in plant dry weight (DW), water content (WC), osmotic potential (Ψs) and leaf water potential (Ψw). Copper treated plants accumulated significantly higher level of Cu in the roots than in the shoots although Cu intake rates decreased with the duration of stress exposure. Additions of NaCl in the absence of Cu excess had no detrimental impact on plant growth. In the presence of Cu excess, NaCl decreased Cu accumulation in roots and stems but had no positive impact on plant growth. Copper induced a large decrease in K concentration in roots and stems as well as a decrease in Ca concentration in the leaves. The impact of Cu and NaCl appeared to be additive on leaf Ψs and leaf quaternary ammonium compounds concentrations. It is concluded that K. virginica exhibits a high bioconcentration factor for Cu which could be, at least partly, responsible for its sensitivity to this toxic element. The impact of stress on K and Ca homeostasis is discussed in relation to ion distribution and presence of mucilage in the plant.